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One quick internet search for the “best diet for weight loss,” will produce a host of sites claiming to have the holy grail of diet products guaranteed to help you lose weight. But is there really a one-size-fits-all diet to suit everyone? The short answer is no.
Before you begin your quest for the best diet for weight loss, make an appointment to speak to your healthcare provider. Crash diets, diet pills, and diet fads can be dangerous and don’t lead to sustainable weight loss. If you and your provider agree that weight loss is a healthy choice, they can help you create a weight loss plan that will be safe, effective, and focus on healthy lifestyle choices over dangerous fads.
How does weight loss work?
Studies show that the most effective weight loss strategy is calorie restriction—in other words, eating fewer calories.
Various diets like intermittent fasting, the Mediterranean diet, low-fat diets, low-carb diets, and more are shown to be effective. Still, the common denominator in a successful diet is taking in fewer calories. Just as people respond differently to medications, people respond differently to diet plans. A diet that helps your friend reduce their caloric intake may not work for you.
Find the method that helps you eat fewer calories in the long run, not just for the short term. Keeping the weight off is much more challenging than initially losing the weight. People who successfully maintain a healthy weight are those who incorporate lifestyle changes and healthy food choices into their daily routines.
Many studies have evaluated different diet plans, sometimes with conflicting results. So, what do we know about dieting? There is no magic solution or “perfect diet.” Before you begin any diet, remember to consult your healthcare provider–calorie restriction can quickly become mentally and physically strenuous and sometimes take a toll on your health. Let’s look at the research behind some popular diet plans.
1. Intermittent Fasting
Intermittent fasting is what it sounds like—you alternate between eating and fasting on a daily or weekly schedule. There are many different intermittent fasting protocols, but the three most popular options are:
- Alternate day fasting (ADF): With ADF, you eat normally one day, fast the next, and keep alternating in this pattern. Fasting can mean a complete fast, where you consume no calories at all, or a period of significantly reduced caloric intake (usually about 25% of your usual calorie intake or ~500 calories)
- Time-restricted feeding (TRF): TRF means that you take in all of your calories during a specific “feeding window” and don’t eat anything outside that window. The most common way to do TRF is to restrict the eating window to eight hours. Most people accomplish this by eating their first meal at noon and finishing their last meal at 8 pm; this is commonly referred to as 16:8 (16 hours of fasting followed by eating all meals within an 8-hour window).
- The 5:2 method: The 5:2 method consists of eating regularly for five days and fasting for two days per week. The fasting days do not need to be consecutive and, as with ADF, may mean eating nothing at all or just eating very few calories.
How does it work?
Intermittent fasting uses the periods when you don’t eat to decrease your overall daily or weekly calorie intake. In other words, since you are eating for shorter periods, you are taking in fewer calories without actually counting calories. There is no specific restriction on what you eat, just when you eat.
Current research shows that intermittent fasting works for weight loss because it helps you decrease how much you eat each day. Intermittent fasting is a popular weight loss option because it does not require you to count calories or follow a complicated diet. This makes it easier to stay on the program over longer periods.
According to research, intermittent fasting is not more effective than diets that use overall calorie restriction to help you lose weight.
People with diabetes or who take antidiabetic medications may be at higher risk of developing hypoglycemia (dangerously low blood sugar levels) and may want to avoid this diet. Healthcare providers may recommend adjusting medications or consulting a specialist.
What to avoid?
When practicing intermittent fasting, it’s easy to binge during eating periods—this defeats the purpose of following the eating plan. During your eating periods, choose healthy food options like whole grains, lean proteins, and high-fiber fruits and vegetables. Also, make sure to drink plenty of water throughout the day.
2. Mediterranean diet
The Mediterranean diet refers to a diet pattern followed by many countries around the Mediterranean sea. The diet promotes eating healthy foods like fruits, vegetables, nuts, legumes, whole grains, and monounsaturated fats like olive oil, with moderate lean meats (seafood, poultry) and dairy products (cheese, milk, eggs). Generally, eating red meat is limited.
How does it work?
By emphasizing fruits, veggies, whole grains, and healthy fats like olive oil, the Mediterranean diet focuses on foods that will keep you fuller for longer, which can result in an overall decrease in your caloric intake.
Olive oil, one of the primary fats in the Mediterranean diet, contains antioxidants and essential fatty acids. Studies suggest that this diet may improve heart health, lower cholesterol, decrease high blood pressure, and lower blood sugar levels. It may also play a protective role in cancer prevention.
The Mediterranean diet may help you lose weight. However, it’s not necessarily better than other diets when used by people who are overweight, have obesity, or are trying to lose weight.
It may be difficult for some people to adhere to the Mediterranean diet plan exclusively, and the diet works best when used consistently. You should keep an eye on how much you eat—too many nuts or olive oil can still lead to weight gain. If you have low iron or low calcium, you may need to eat more iron-rich foods or dairy products than is typically recommended on the Mediterranean diet.
Lastly, some versions of the Mediterranean diet recommend a glass of red wine daily. It may not be appropriate for certain people to follow this guideline, like those who are pregnant or who have liver disease.
What to avoid
Like any diet, moderation is key for the Mediterranean diet to be effective. The bulk of your foods should be vegetables, fruits, and whole grains. Fats, especially olive oil, are a significant part of the diet—but take care not to overdo fats, nuts, and red wine.
3. DASH diet
Dietary Approaches to Stop Hypertension, or DASH diet, is a diet designed to help people lower their high blood pressure (hypertension). The DASH diet emphasizes eating fruits, vegetables, beans, whole grains, low-fat dairy products, and lean proteins, like chicken and fish. It also limits red meat, refined sugars, saturated fat, and sodium (no more than one teaspoon, or 2300 mg, of sodium per day).
How does it work?
The DASH diet limits your sodium intake, which helps lower your blood pressure. When you take in sodium, your body holds on to water. The more water you hold onto, the higher your blood pressure.
This diet also encourages you to eat whole grains, lean proteins, and lots of vegetables and fruits. These foods can help you feel fuller and eat less over the course of the day.
Numerous studies show that not only does the DASH diet help lower blood pressure, but it can also help lower blood sugar, triglycerides, and cholesterol levels. It may reduce your risk of developing colon cancer and help with other medical conditions like liver disease, heart failure, and celiac disease.
One of the basic tenets of the DASH diet is limiting your sodium intake. According to the FDA, more than 70% of the average American’s daily sodium intake comes from processed and prepackaged foods, not your salt shaker. Salt makes foods taste better, and some people who start a low sodium diet find that their food tastes bland. Bland food might make it hard to stick to the DASH diet.
Another disadvantage is that there are not many “convenient” food options when following the DASH diet. As mentioned, prepackaged foods tend to have more sodium. The effort required to prepare appropriate low-sodium foods can be a barrier for many people.
While DASH is considered a healthy diet plan, people with certain medical conditions like uncontrolled diabetes, kidney disease, heart failure, etc., may need to modify their DASH diet plan.
What to avoid
The main thing to avoid in the DASH diet is excess dietary sodium—this requires more than just taking it easy with the salt shaker. Most of the sodium you eat comes from prepackaged food, as previously mentioned, but don’t forget about dining out–around 30% of the average American’s sodium intake comes from eating out at restaurants and fast-food chains. You should avoid or limit dining out on the DASH diet.
4. Ketogenic diet
The ketogenic or “keto” diets encourage you to limit your carbohydrate intake to between 20–50 grams per day and eat more fats and proteins. This very low-carbohydrate and high-fat diet seems to be effective for weight loss—at least in the short term.
How does it work?
The theory behind the keto diet is that by decreasing your carb intake, you force your body into a state of nutritional ketosis where your liver converts fats into ketones, which are then used as an energy source in place of carbs. In ketosis, your body switches to fat-burning mode. Some people on a ketogenic diet may feel less hungry and decrease their overall calorie intake, promoting further weight loss without counting calories.
Many people who start a low-carb keto diet notice rapid weight loss in the first two weeks—up to 10 lbs in two weeks or less. This is likely due to a diuretic effect where much of that initial weight loss is water weight, followed by fat loss.
One disadvantage of ketogenic diets is that many people find it tough to stay on this restrictive diet—long-term weight loss may be difficult to achieve.
The first few weeks of the diet are often accompanied by the “keto flu,” which includes symptoms of fatigue, irritability, dizziness, bad breath, nausea, vomiting, headache, diarrhea, and constipation. This diet can also lead to long-term side effects like fatty liver disease, low blood protein levels, kidney stones, and vitamin and mineral deficiencies.
If you have diabetes, you may need your healthcare provider to adjust your medications to prevent dangerously low blood sugar while on this diet. Lastly, people with pancreatitis, liver failure, problems metabolizing fat, or certain enzyme deficiencies should not follow the keto diet.
What to avoid
Avoid dehydration and make sure that you are drinking plenty of fluids on the ketogenic diet—this will help with some of the keto flu symptoms. Don’t follow this diet for more than 6–12 months, and then engage in a gradual transition back to a standard diet.
5. Paleolithic diet
The paleolithic diet, also known as the paleo, hunter-gatherer, or stone-age diet, attempts to recreate the diet that our “cavemen” ancestors consumed, including:
- Plants including tubers, seeds, nuts, wild-grown barley that was pounded into flour, and legumes
- Meat including fish, shellfish, lean beef, pork, and poultry, along with game animals
- Fruits including berries, citrus fruits, and melons
- Non-starchy vegetables including greens, peppers, onions, etc.
- Healthy fats including nuts, seeds, and olive oil
Refined fats and sugars, as well as processed foods, are not allowed.
How does it work?
The paleo diet’s high protein and low carbohydrate focus are likely why it works. The high protein and high-fiber nature of permitted foods help you stay fuller longer, eat less overall, and lose weight.
Several studies show short-term weight loss on the paleo diet.
However, there is conflicting research on whether these effects are any better than other diets, and very few studies look at the long-term health benefits of the paleo diet.
Like the keto diet, paleo diets are tough to maintain long-term because they are so restrictive. Buying all organic produce and avoiding processed foods can also be expensive. Another downside of the paleo diet is a potential risk for vitamin D, calcium, and iodine deficiencies.
What to avoid
Remember that the paleo diet tries to mimic the foods that were available to our hunter-gatherer ancestors before the onset of animal domestication. Therefore, you should avoid cultivated products, like dairy, most oils, many kinds of cereal, salt, and refined sugars. The paleo diet also recommends organic, grass-fed meats.
6. Plant-based diet
Plant-based diets encourage you to eat more fruits, vegetables, beans, whole grains, nuts, and vegetable oils while avoiding or limiting animal products like meat, dairy, and fish. Plant-based diets can vary greatly; some only exclude meat (vegetarian) while others may exclude all animal products (vegan), and others fall somewhere in between.
How does it work?
Like many other diets on this list, plant-based diets work by encouraging you to eat high-fiber foods like fruits, vegetables, and whole grains. These types of foods are not digested as quickly as sugary foods, so you feel full longer. Feeling full helps you eat less and lose weight. Of course, this won’t work if your plant-based diet consists solely of potato chips and milkshakes—you still need to make healthy food choices.
Some studies show that a plant-based meal plan can help you lose weight; however, other studies indicate that this weight loss is not significant compared to non-vegetarian diets.
It is important to note that cutting out all animal products can lead to deficiencies of protein, iron, zinc, calcium, and vitamins D and B12. If you plan to switch to a plant-based diet, consult with your healthcare provider to make sure you are still getting all the necessary nutrients.
What to avoid
The foods you avoid will depend on the type of plant-based diet plan you choose. Flexitarian plans allow for meat in limited amounts, while a pescatarian diet allows fish and seafood. Following a vegan diet is even more strict, with no animal products allowed, including eggs and dairy products.
WW, formerly known as Weight Watchers, is a popular weight loss program that incorporates food tracking, counseling, and limiting the amount of food you eat each day.
How does it work?
WW focuses on modifying behaviors and diet while increasing physical activity—all to help you lose weight. For their in-person program, you attend weekly meetings led by a WW Lifetime member who has successfully completed the program and received training from the company. You can also track your food and activity using their app.
WW helps you control your calorie intake by assigning point values to different foods and giving you a personalized “allowance” of points per day. You are free to use up those points any way you want, but the idea is not to go “over-budget.” There is also a support community available through the WW app, group sites, etc.
In a literature review of commercial diet plans, WW participants consistently lost more weight (2.6% more weight loss) after one year than people who only received education about weight loss.
WW focuses not only on foods but also on behavioral changes, like increasing physical activity, which can help you keep the weight off. Also, by attending the meetings, you can talk to other people who struggle with similar issues and can support you with unique solutions to your weight loss hurdles.
WW comes with the additional cost of paying for the program, starting at around $20 per month.
What to avoid
Overall, the goal of WW is to help you create a habit of healthy eating. With that said, there are no specific foods you need to avoid. Each food has a point value—more nutritious foods “cost” fewer points than unhealthy foods, like pizza or French fries. If you consume unhealthy foods, you’ll be limited on how much you can eat for the rest of the day (i.e., you’ll have spent your food point allowance).
How to choose a diet plan
Despite all of the research available, there is no single diet that works for everyone to lose weight. Dieting consists of two phases: losing weight and keeping it off long-term. Highly restrictive diets may jump-start your weight loss, but don’t usually work to keep the weight off long-term. When looking for a safe and successful dieting plan, look for the following:
- A plan should promote changes that are sustainable in the long term.
- Avoid diets that eliminate entire food groups or are too restrictive, claim significant weight loss in a very short amount of time, or tell you that you can avoid exercising.
- For a diet to work, you need to decrease your calorie intake.
- Have a way to monitor and self-check, like weekly weigh-ins, food tracking, etc.
- Aim for diets that emphasize whole foods like fruits, vegetables, whole grains, and lean protein.
Avoid yo-yo dieting (losing and regaining weight) and look for a diet that encourages healthy lifestyle changes, like eating whole foods and increasing physical activity, to stay healthy and keep the weight off. Aim for slow and steady weight loss (about 1–2 lbs per week).
Experts recommend that people who are overweight or have obesity start with a weight loss goal of 5–10% of their starting weight over six months–this translates to a 10–20 lbs weight loss over six months for someone who weighs 200 lbs at the start of the diet.
Losing weight can be a daunting task. It’s easy to become discouraged. Build a support system of friends, family, and the online community and know you’re not alone. Instead of centering your goal around losing weight, refocus on becoming healthy–a healthy weight decreases your risk of heart disease, type 2 diabetes, and high blood pressure. Work with your healthcare provider to find a weight management strategy that works for you.
If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
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Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.